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sched_ext: Don't kick CPUs running higher classes

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When a sched_ext scheduler tries to kick a CPU, the CPU may be running a
higher class task. sched_ext has no control over such CPUs. A sched_ext
scheduler couldn't have expected to get access to the CPU after kicking it
anyway. Skip kicking when the target CPU is running a higher class.

Reviewed-by: Andrea Righi <arighi@nvidia.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Tejun Heo 2025-10-22 10:56:27 -10:00
parent 2dbbdeda77
commit a9c1fbbd6d
1 changed files with 8 additions and 3 deletions
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11
kernel/sched/ext.c
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@ -5122,18 +5122,23 @@ static bool kick_one_cpu(s32 cpu, struct rq *this_rq, unsigned long *pseqs)
{
struct rq *rq = cpu_rq(cpu);
struct scx_rq *this_scx = &this_rq->scx;
const struct sched_class *cur_class;
bool should_wait = false;
unsigned long flags;
raw_spin_rq_lock_irqsave(rq, flags);
cur_class = rq->curr->sched_class;
/*
* During CPU hotplug, a CPU may depend on kicking itself to make
* forward progress. Allow kicking self regardless of online state.
* forward progress. Allow kicking self regardless of online state. If
* @cpu is running a higher class task, we have no control over @cpu.
* Skip kicking.
*/
if (cpu_online(cpu) || cpu == cpu_of(this_rq)) {
if ((cpu_online(cpu) || cpu == cpu_of(this_rq)) &&
!sched_class_above(cur_class, &ext_sched_class)) {
if (cpumask_test_cpu(cpu, this_scx->cpus_to_preempt)) {
if (rq->curr->sched_class == &ext_sched_class)
if (cur_class == &ext_sched_class)
rq->curr->scx.slice = 0;
cpumask_clear_cpu(cpu, this_scx->cpus_to_preempt);
}